Data on wheat tolerance to heat

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Data were collected from irrigated field experiments conducted across three locations between 2018 and 2020. Twenty-five spring wheat genotypes (including Australian cultivars, CIMMYT heat-tolerant germplasm, and MR-NAM donor parents) were evaluated under the photoperiod-extension method (PEM) and in adjacent conventional plot trials at two sowing times (s1, standard and s2, late sowing) to vary post-flowering heat exposure. In PEM trials, approximately 20 stems per replicate per genotype were tagged at flowering, and spikes were manually harvested at maturity (spike-level measurements of IGW and GPC), while conventional plots were machine harvested at maturity (crop-level measurements of grain number, IGW, yield and GPC). Weather data was recorded at each site using on-site stations, and heat exposure was quantified as post-flowering hot days (Tmax > 32°C) during 0–500°Cd after flowering. Spatial correction (SpATS) and linear regression analyses were used to quantify reaction norms and estimate genotype-specific heat tolerance thresholds.